Blade Flow Deflector

ABSTRACT

An airfoil blade assembly including a blade which includes a lift generating section with a first profiled body defined between a pressure surface and a suction surface. The first profiled body extends from a first leading edge to a first trailing edge with a first chord extending form the first leading edge to the first trailing edge and being perpendicular to the radial direction. At least one flow deflector extends along either the pressure surface or the suction surface within the lift generating section of the blade. The at least one flow deflector defines a second profiled body extending between a second leading edge and a second trailing edge with a second chord extending between the second leading edge and the second trailing edge. The second profiled body defines an outer surface facing away from respective pressure surface or suction surface along which the flow deflector extends.

BACKGROUND

This application claims the benefit of U.S. Provisional Application No.61/909,733, filed Nov. 27, 2014, the contents of which are incorporatedherein by reference.

STATEMENT OF THE TECHNICAL FIELD

The present disclosure relates to blades. More specifically, the presentdisclosure relates to blades having incorporated flow deflectors.

DESCRIPTION OF THE RELATED ART

Wind turbines produce power proportional to the swept area of theirblades, and the amount of air flow passing over the blades at any giventime. Various design choices such as rotor diameter, blade length andload limitations are considered during design and fabrication of a windturbine. Longer blades provide for more energy production in low winds.However, longer blades require more materials, higher manufacture andtransportation costs, larger and more robust rotor design to support theadded weight of the longer blades, and failsafe systems for preventingpotential damage to the turbines in high wind situations as the longerblades may produce damaging levels of torque at high wind speeds.

Conversely, using shorter blades has its own set of drawbacks. Forexample, in low winds shorter blades may not have enough surface area toproduce enough torque to move the rotor, thereby producing no power.

Regardless of size, all wind turbine blades are limited in overallefficiency due to various resulting properties of the air flow. Due tothe rotational movement of the blades during operation, at least aportion of the air flow impacting the blade is converted to a radialcomponent moving about the length of the blade from the root toward thetip of the blade. FIG. 1 illustrates a standard wind turbine 10 with amast 12 supporting a hub 14 from which a plurality of blades 16 aresupported. The mass of air affected by the turbine forms a stream tubeas the wind must slow down due to energy extracted by the turbine. WindW directed at the turbines will have an initial area as indicated by thecircle 18. As the wind W reaches the blades 16, the air flow has twocomponents, namely an axial flow W_(A) and a radial flow W_(R), with thearea of the wind flow expanding radially as indicated by circle 20 dueto the conservation of mass flow rate along the stream tube. The flowcontinues to expand radially downstream, as indicated by the increasedarea at circle 22, since the pressure in the wake must return to theatmospheric pressure after a pressure drop experienced by passing thoughthe rotor disc. Based on the conservation of momentum, this radial flowW_(R) reduces the efficiency of the turbine since it creates a radialforce from the available total force from the wind. This radial force isnot contributing to any torque or power produced by the rotor.

The present disclosure addresses these and other similar problemsresulting from conventional blade design. It allows the blade to convertpart of that radial force into a tangential force by redirecting theradial flow W_(R), thereby increasing the torque and power extracted bythe turbine.

SUMMARY

In at least one embodiment, the present disclosure describes an airfoilblade assembly including a blade extending in a radial direction from aroot towards a tip. The blade includes a lift generating section with asfirst profiled body defined between a pressure surface and a suctionsurface. The first profiled body extends from a first leading edge to afirst trailing edge with a first chord extending form the first leadingedge to the first trailing edge and being perpendicular to the radialdirection. At least one flow deflector extends along either the pressuresurface or the suction surface within the lift generating section of theblade. The at least one flow deflector defines a second profiled bodyextending between a second leading edge and a second trailing edge witha second chord extending between the second leading edge and the secondtrailing edge. The second profiled body defines an outer surface facingaway from respective pressure surface or suction surface along which theflow deflector extends.

In at least one embodiment, the present disclosure describes a windturbine assembly including a hub configured to rotate in a direction ofrotation and a plurality of blade assemblies attached to the hubassembly and including flow deflectors attached to the blades. The flowdeflectors are configured so as to alter the incident airflow so that anadditional force is produced in the direction of rotation and anadditional power is generated. The deflectors are not limited to windturbines but may be positioned on blades used in various applications,for example, helicopters, hydro turbines, airplane wings, engines,propellers, and industrial turbines. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described with reference to the following drawingfigures, in which like numerals represent like items through thefigures, and in which:

FIG. 1 is a perspective view of an example prior art wind turbine andthe corresponding typical air flow thereabout.

FIG. 2 is a perspective view of an example of a wind turbine havingblades incorporating flow deflectors in accordance with an embodiment ofthe present disclosure.

FIG. 3 is a perspective view of an example blade incorporating flowdeflectors in accordance with an embodiment of the present disclosure.

FIG. 4 is a cross-sectional view along the line 4-4 in FIG. 3.

FIG. 5 is a cross-sectional view along the line 5-5 in FIG. 3.

FIG. 6 is a top plan view of a portion of the blade of FIG. 3.

FIG. 7 is a top plan view of a blade incorporating a flow deflector inaccordance with an embodiment of the disclosure and illustrating theresultant forces thereon.

FIG. 8 is a top plan view of another blade incorporating a flowdeflector in accordance with an embodiment of the disclosure andillustrating the resultant forces thereon.

DETAILED DESCRIPTION

This disclosure is not limited to the particular systems, devices andmethods described, as these can vary. The terminology used in thedescription is for the purpose of describing the particular versions orembodiments only, and is not intended to limit the scope.

As used in this document, the singular forms “a,” “an,” and “the”include plural references unless the context clearly dictates otherwise.Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art. As used in this document, the term “comprising” means“including, but not limited to.”

The present disclosure relates to deflectors positioned on either thepressure surface or suction surface of a blade. The blades will bedescribed herein in conjunction with a wind turbine, however, thedisclosure is not limited to such and the deflectors may be positionedon blades used in various applications, for example, helicopters, hydroturbines, airplane wings, engines, propellers, and industrial turbines.

Referring, to FIGS. 2-6, blades 30 incorporating flow deflectors 50 inaccordance with an embodiment of the disclosure will be described. Theblades 30 are illustrated positioned on the hub 14 of a wind turbine 10with the hub 14 supported by a mast 12. The hub 14 and blades 30 rotateabout an axis of rotation AR. Each blade 30 extends radially along aradial axis RA from a root 40 to a tip 42. Each blade 30 generallyincludes three sections, namely a root section 32, a transition section36 and a lift generating section 34. The root section 32 connects theblade 30 to the hub 14. The lift generating segment 34 is furthest fromthe hub 14 and includes a profiled body 37 extending between a pressuresurface 39 and a suction surface 38. The profiled body 37 extendsbetween a leading edge 31 and a trailing edge 33. A chord 35 is definedfrom the leading edge 31 to the trailing edge 33 and is perpendicular tothe radial axis RA. The chord 35 has a length L and the profile body 37has a height H.

One or more flow deflectors 50, 50′ are provided along the pressuresurface 39, the suction surface 38 or both surfaces within the liftgenerating section 34. The flow deflectors 50, 50′ may be positionedproximate the leading edge 31, the trailing edge 33 or anywhere inbetween. In the illustrated embodiment, a pair of flow deflectors 50 arepositioned along the suction surface 38 of each blade 30 and a singleflow deflector 50′ is positioned along the pressure surface 39 of eachblade 30. The number and position of the deflectors 50, 50′ are notlimited to the illustrated embodiment and can be selected depending onthe configuration of the blade 30 and the operating environment. Thedeflectors 50, 50′ may be formed integral with blade 30 or may be formedseparately and attached thereto. For example, the deflectors 50, 50′ maybe attached to the blade 30 utilizing aerospace double-sided tape with athickness on the order of micrometers or utilizing small flat headrivets to minimize drag. Various other attachment mechanisms may beutilized. Additionally, the deflectors 50, 50′ may be provided along thesurfaces during original manufacture of the blades 30 or may be attachedto existing blades 30 in a retro-fit fashion. Furthermore, thedeflectors 50, 50′ may be adjustably positioned such that the positionand orientation may be adjusted to correspond to current operatingcondition (e.g. more or less wind).

Each flow deflector 50, 50′ has a profile body 52 extending from aleading edge 51 to a trailing edge 53. A chord 55 is defined from theleading edge 51 to the trailing edge 53 and is perpendicular to theradial axis RA or at angle α thereto as described hereinafter. The chord55 has a length l and the profile body 52 has a height h and a width w.Each profile body 52 has an outer surface 54 and a contact surface 56,56′ and defines a streamline body, such as a flat plate or a thinairfoil. The deflectors 50, 50′ generally extend such that they extendbeyond the boundary layer flow over the blade 30.

The flow deflectors 50, 50′ may be sized proportional to the blade 30.For example, the flow deflectors may have a chord length l which isbetween ⅛ to 1 that of the blade chord length L, and more preferablybetween ¼ to ½ of the length L. Also, the flow deflectors may have aheight h which is between 1/10 to 1 that of the blade height H, and morepreferably between ⅛ to ½ of the height H. Also, the width w of the flowdeflections may also be proportional to the chord length L of the blade30, with a width w between about 1-10% of the blade chord length L. Itis understood that if more than one deflector 50, 50′ is positioned onthe blade 30, the deflectors 50, 50′ may have different configurations.For example, the suction surface deflectors 50 may be sized differentlythan the pressure side deflectors 50′, however, it is also possible thatthere may be differences in configuration between multiple suctionsurface deflectors 50 or multiple suction pressure deflectors 50′.

Referring to FIG. 6, each of the deflectors 50, 50′ may be positioned atan angle α relative to the blade 30. More specifically, the chord 55 ofeach deflector may be at an angle α relative to the chord 35 of theblade 30. The angle α may be between about −5° and 45° and morepreferably between about 0° and 15°. If multiple deflectors 50, 50′ arepositioned along either surface 38, 39, they may be at different anglesα. The deflectors 50, 50′ are spaced from one another in the directionof the radial axis RA by a distance D. The distance D may vary betweendeflectors 50, 50′ on a given surface and between surfaces. As oneexample, the distance D may be equal to the chord length L.

Referring to FIGS. 7 and 8, an illustration of resultant increasedefficiency from the flow deflectors 50, 50′ will be described. FIG. 7shows the moment, M+M_(D1), and force, F_(T)+F_(D1), generated by ablade 30 with a deflector 50. The additional force contribution by thedeflector to the turbine blade is F_(D1). This force generates anadditional moment M_(D1) which contributes to the total power generatedby the turbine FIG. 8 shows an in-plane curved wind turbine blade 30′with a flow deflector 50. The configuration of the lift generatingsection 36′ is distinct from that of the blade 30 in FIG. 7. Thisconfiguration of blade with the flow deflector 50 generates anadditional torque M_(D2), that contributes to the power generated and itis due to the normal force F_(D2) created by the deflector 50.

Integrating the deflectors 50, 50′ onto existing turbines, orincorporating their design into new turbines will increase the overallefficiency of the turbines. The deflectors may act as passive flowcontrollers, not requiring any additional control or monitoringequipment. By introducing the flow deflectors at several positions alongthe blade's length, the radial component of velocity of the incoming airflow may be redirected to produce an additional amount of torque on therotor, thereby increasing the overall power produced by the turbine.

These and other advantages of the present invention will be apparent tothose skilled in the art from the foregoing specification. Accordingly,it will be recognized by those skilled in the art that changes ormodifications may be made to the above-described embodiments withoutdeparting from the broad inventive concepts of the invention. It shouldtherefore be understood that this invention is not limited to theparticular embodiments described herein, but is intended to include allchanges and modifications that are within the scope and spirit of theinvention as defined in the claims.

1. An airfoil blade assembly comprising: a blade extending in a radialdirection from a root towards a tip, the blade including a liftgenerating section with a first profiled body defined between a pressuresurface and a suction surface, the first profiled body extending from afirst leading edge to a first trailing edge with a first chord extendingform the first leading edge to the first trailing edge and beingperpendicular to the radial direction; a plurality of flow deflectorsextending along either the pressure surface or the suction surfacewithin the lift generating section of the blade, the plurality of flowdeflectors defining a second profiled body extending between a secondleading edge and a second trailing edge with a second chord extendingbetween the second leading edge and the second trailing edge, the secondprofiled body defining an outer surface facing away from respectivepressure surface or suction surface along which the plurality of flowdeflectors extend; wherein the plurality of flow deflectors arepositioned along a length of the blade so that a radial component ofvelocity of an incoming airflow is redirected to produce an additionalamount of torque on a rotor, thereby increasing overall power producedby a turbine incorporating the airfoil blade assembly.
 2. The airfoilblade assembly according to claim 1 wherein the second chord is at anangle α of between −5° and 45° relative to the first chord.
 3. Theairfoil blade assembly according to claim 1 wherein the second chord isat an angle α of between 0° and 15° relative to the first chord. 4.(canceled)
 5. The airfoil blade assembly according to claim 1 whereinthe plurality of flow deflectors are separated from one another by agiven distance.
 6. The airfoil blade assembly according to claim 5wherein the given distance is equal to a length of the first chord. 7.(canceled)
 8. The airfoil blade assembly according to claim 1 whereinthe plurality of flow deflectors are positioned along the blade betweenthe first leading edge and the first trailing edge.
 9. The airfoil bladeassembly according to claim 1 wherein the first profile body has a firstheight and the second profile body has a second height and wherein thesecond height is between 1/10 to 1 that of the first height.
 10. Theairfoil blade assembly according to claim 1 wherein the first profilebody has a first height and the second profile body has a second heightand wherein the second height is between ⅛ to ½ that of the firstheight.
 11. The airfoil blade assembly according to claim 1 wherein thesecond profile body has a width that which is equal to approximately1-10% a length of the first chord.
 12. The airfoil blade assemblyaccording to claim 1 wherein the plurality of flow deflectors are formedintegrally with the first profile body.
 13. The airfoil blade assemblyaccording to claim 1 wherein the plurality of flow deflectors are formedseparately from the first profile body and are attached thereto.
 14. Theairfoil blade assembly according to claim 1 wherein the plurality offlow deflectors are attached to the first profile body utilizingaerospace double-sided tape.
 15. The airfoil blade assembly according toclaim 1 wherein the plurality of flow deflectors are attached to thefirst profile body utilizing flat head rivets.
 16. The airfoil bladeassembly according to claim 1 wherein the plurality of flow deflectorsare adjustably connected to the profile body.
 17. The airfoil bladeassembly according to claim 1 wherein the blade has an in-plane curvedconfiguration.
 18. A turbine assembly comprising: a hub configured torotate in a direction of rotation; a plurality of blade assembliesaccording to claim 1 attached to the hub assembly, wherein the pluralityof flow deflectors are configured so as to alter the incident airflow sothat an additional force is produced in the direction of rotation and anadditional power is generated.
 19. A hydrofoil blade assemblycomprising: a blade extending in a radial direction from a root towardsa tip, the blade including a lift generating section with a firstprofiled body defined between a pressure surface and a suction surface,the first profiled body extending from a first leading edge to a firsttrailing edge with a first chord extending form the first leading edgeto the first trailing edge and being perpendicular to the radialdirection; a plurality of flow deflectors extending along either thepressure surface or the suction surface within the lift generatingsection of the blade, the plurality of flow deflectors defining a secondprofiled body extending between a second leading edge and a secondtrailing edge with a second chord extending between the second leadingedge and the second trailing edge, the second profiled body defining anouter surface facing away from respective pressure surface or suctionsurface along which the plurality of flow deflectors extend; wherein theplurality of flow deflectors are positioned along a length of the bladeso that a radial component of velocity of an incoming water flow isredirected to produce an additional amount of torque on a rotor, therebyincreasing overall power produced by a turbine incorporating thehydrofoil blade assembly.
 20. The hydrofoil blade assembly of claim 19wherein the plurality of flow deflectors are separated from one anotherby a given distance.
 21. The hydrofoil blade assembly of claim 19wherein the plurality of flow deflectors are formed integrally with thefirst profile body.
 22. The hydrofoil blade assembly of claim 19 whereinthe plurality of flow deflectors are formed separately from the firstprofile body and are attached thereto.
 23. A turbine assemblycomprising: a hub configured to rotate in a direction of rotation; aplurality of blade assemblies according to claim 19 attached to the hubassembly, wherein the plurality of flow deflectors are configured so asto alter the incident water flow so that an additional force is producedin the direction of rotation and an additional power is generated.